The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 100 32 251.4, filed on Jul. 3, 2000, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a machine for producing a fibrous material web, in particular a tissue or hygiene paper web, having at least one shoe press including a drying cylinder and one shoe press unit for forming a pressing nip that is elongated in the web travel direction, with the fibrous material web being guided through the elongated pressing nip along with a water-permeable continuous carrying belt and with the carrying belt being guided over at least one suctioned apparatus before the shoe press in the web travel direction.
The instant invention also relates to a process for producing a fibrous material web, in particular a tissue or hygiene paper in which the fibrous material web, along with a water-permeable continuous carrying belt, is guided through at least one elongated pressing nip of a shoe press including a drying cylinder and a shoe press unit and the carrying belt is guided over at least one suctioned apparatus before the shoe press in the web travel direction.
2. Discussion of Background Information
A machine of the type mentioned at the outset is disclosed in EP-A-0 926 296.
In a tissue machine known from WO 97/03247, a relatively large and expensive TAD (through air drying) unit is provided instead of a shoe press.
The present invention provides a device and process of the type mentioned at the outset with which the dry content of the tissue is further increased in a volume-saving and cost-effective manner and, correspondingly, the production of tissue can be made more economical.
With regard to the machine, the instant invention includes a hood subjected to overpressure that is assigned to the suctioned apparatus in order to support the underpressure effect of the suctioned apparatus.
Via the hood, which is subjected to overpressure and can be a smaller hood in particular, the underpressure effect of the suctioned apparatus is supported, which improves the runnability of the tissue web, especially at higher speeds. Thus, such a hood can be used particularly advantageously where the speeds are greater than approximately 1800 m/min, preferably greater than approximately 2000 m/min, and in particular greater than approximately 2200 m/min.
Preferably, the carrying belt is guided over the suctioned apparatus along with the fibrous material web, with the fibrous material web lying on the outside.
In a preferred practical embodiment of the machine according to the invention, the suctioned apparatus includes a suction roll.
It is advisable to provide overheated steam and/or dry and/or moist hot air as an overpressure fluid for the hood. The heating of the fibrous material web caused thereby contributes substantially to increasing dewatering performance in the subsequent elongated pressing nip. Here, even an increase in web moisture by the moist hot air can be accepted. Moreover, the steam and the dry hot air also intensify the drying in the region of the suctioned apparatus.
It is advantageous for an additional suctional element to be provided between the suctioned apparatus and the shoe press. In this manner, the dry content is increased further because this additional suction element prevents the back flow of the water from the carrying belt into the tissue web caused by capillary action. This suction element can, in particular, include a suction box.
The shoe press unit advantageously has several pressing zones, at least crosswise to the web travel direction, that are adjustable independently of one another.
In a useful practical embodiment, the drying cylinder is provided as a tissue or Yankee drying cylinder from which the fibrous material web can be scraped after drying has occurred by a crepe doctor.
It is advantageous for the carrying belt to be provided in a forming section for accepting the fibrous stock suspension from a headbox.
Here, it is advisable to guide the carrying belt as the inner belt over a forming roll or the like, over which at least one continuous outer wire is guided.
In a useful practical embodiment of the machine according to the invention, a felt belt is provided as the carrying belt and/or the inner belt.
Thus, especially an embodiment as a crescent former with a felt belt provided as an inner wire is possible. The use of an additional suction element arranged between the suctioned apparatus and the shoe press is particularly advantageous in such an arrangement.
In another useful embodiment, a wire belt, for example, a dewatering belt, is provided as the carrying and/or inner belt. In this case, an additional continuous felt belt arranged between the carrying belt and the shoe press unit is guided along with the fibrous material web and the carrying belt through the elongated pressing nip, whereby markings are prevented and dewatering is supported or even deliberately produced, in particular when the carrying belt is an imprinting wire or felt.
The shoe press unit is preferably provided with a water-impermeable circulating endless pressing belt. Here, the shoe press unit can, in particular, be formed by a shoe press roll with a pressing jacket, preferably a water-impermeable pressing jacket.
Otherwise, the shoe press can, in particular, be embodied as described in DE-A-99 125 789.0, the disclosure of which is expressly incorporated by reference herein in its entirety.
The process according to the invention is correspondingly characterized in that the underpressure effect of the suctioned apparatus is supported by an overpressurized hood that is assigned to one of the suctioned apparatuses.
The arrangement and process according to the invention can be used in particular in tissue machines of various embodiments, for example, for suction breast roll formers, double wire formers, crescent formers, fourdrinier wires, etc. Moreover, a combination with through air drying concepts is advantageous.
The present invention is directed to a machine for producing a fibrous material web that includes at least one shoe press having at least one drying cylinder and a shoe press unit which are arranged to form a pressing nip elongated in a web travel direction. At least one suctioned apparatus is arranged before the at least one shoe press relative to the web travel direction, and a water-permeable continuous carrying belt is arranged to guide the fibrous material web over the at least one suctioned apparatus and through the elongated pressing nip. A hood subjected to an overpressure is assigned to the suctioned apparatus and is arranged to support an underpressure effect of the at least one suctioned apparatus.
In accordance with a feature of the instant invention, the fibrous material web can include a tissue or hygiene paper web.
According to another feature of the invention, as the carrying belt guides the fibrous material web over the suctioned apparatus, the carrying belt can be arranged between the fibrous material web and the suctioned apparatus.
The present invention also provides that the suctioned apparatus may include a suction roll.
The hood can contain an overpressure fluid comprising at least one of overheated steam and dry and/or moist hot air.
Further, a suction element can be positioned between the suctioned apparatus and the at least one shoe press. The suction element can include a suction box.
The at least one shoe press unit may include a plurality of pressing zones arranged crosswise to the web travel direction. Further, the plurality of pressing zones may be controllable independently of one another.
Moreover, the drying cylinder can include a tissue or Yankee drying cylinder, and the machine further may further include a crepe doctor arranged to remove the fibrous material web from the tissue or Yankee drying cylinder after drying.
In accordance with still another feature of the instant invention, the machine may include a forming section in which the carrying belt can be arranged to accept a fibrous stock suspension from a headbox.
Still further, a forming roll and a continuous outer wire may be provided. The carrier belt can also guided over the forming roll as an inner belt over a forming roll in relation to the continuous outer wire. Further, the inner belt may include a felt belt, a wire belt, a dewatering belt, or an imprinting member.
According to a still further feature of the present invention, the carrier belt can include a felt belt, a wire belt, a dewatering belt, or an imprinting member.
The machine in accordance the instant invention can further include an additional continuous felt belt which is arranged between the carrying belt and the shoe press unit and which is guided through the elongated pressing nip along with the fibrous material web and the carrying belt.
The one shoe press unit may include a water-impermeable continuous, circulating press belt.
Moreover, the shoe press unit can include a shoe press roll with a pressing jacket. The pressing jacket may include a water-impermeable pressing jacket.
The present invention is directed to a process for producing a fibrous material web in an apparatus including a water-permeable continuous carrying belt, at least one shoe press having an elongated pressing nip formed between a drying cylinder and a shoe press unit, at least one suctioned apparatus, which includes a hood, arranged before the at least one shoe press unit relative to a web travel direction, and a carrying belt guided over the at least one suctioned apparatus. The process includes guiding the fibrous material web and the carrying belt through the elongated pressing nip, and supporting an underpressure effect of the suctioned apparatus by creating an overpressure in the hood.
According to a feature of the instant invention, as the carrying belt guides the fibrous material web over the suctioned apparatus, the carrying belt can be positioned between the suctioned apparatus and the fibrous material web.
In accordance with another feature of the present invention, the suctioned apparatus may include a suction roll.
According to the process of the invention, the overpressure in the hood can be created by an overpressure fluid comprising at least one of overheated steam and dry and/or moist hot air.
Moreover, the apparatus can further include a suction element positioned between the suctioned apparatus and the at least one shoe press, and process may further include suctioning the carrying belt and fibrous material web guided over the suction element.
In accordance with still another feature of the present invention, the suction element may include a suction box.
Further, the shoe press unit can include a plurality of pressing zones arranged at least crosswise to the web travel direction, and the process may further include independently controlling the plurality of pressing zones.
The drying cylinder can include a tissue or Yankee drying cylinder, and the process may include scraping the fibrous material web from the tissue or Yankee drying cylinder after drying. Further, the apparatus can include a crepe doctor and the process may further include scraping the fibrous material web from the tissue or Yankee drying cylinder after drying with the crepe doctor.
In accordance with a further feature of the invention, the apparatus can include a forming section and the carrying belt can be guided through the forming section, and the process may include accepting a fibrous material suspension from a headbox on the carrying belt.
Still further, the apparatus may include a forming roll with a continuously outer wire, and the carrying belt may be guided over the forming roll as an inner wire between the continuous outer wire and the forming roll, and the process can include supplying a fibrous material suspension between the inner wire and the outer wire. Further, the inner belt may include a felt belt, a wire belt, a dewatering belt, or an imprinting member.
Further, in the process of the instant invention, the carrier belt may include a felt belt, a wire belt, a dewatering belt, or an imprinting member.
The apparatus can include an additional continuous felt belt arranged between the carrying belt and the shoe press unit in the elongated pressing nip, and the process may include guiding the fibrous material web through the elongated pressing nip along with the carrying belt and the additional continuous felt belt.
According to the process of instant invention, the shoe press unit can include a water-impermeable pressing belt.
In accordance with a feature of the process of the present invention, the shoe press unit can include a pressing jacket. Further, the pressing jacket may include a water-impermeable pressing jacket.
The present invention is directed to an apparatus for producing a fibrous material web that includes at least one shoe press including at least one drying cylinder and a shoe press unit which are arranged to form a pressing nip elongated in a web travel direction. At least one suctioned apparatus is arranged before the at least one shoe press relative to the web travel direction, and an overpressure device is associated with the at least one suctioned apparatus arranged to support an underpressure effect of the at least one suctioned apparatus.
According to a feature of the instant invention, the overpressure device may include a hood subjected to an overpressure, which can be arranged to surround at least a portion of the at least one suctioned apparatus.
In accordance with yet another feature of the present invention, the overpressure device can include an overpressure fluid comprising at least one of overheated steam and dry and/or moist hot air.
The present invention is directed to a process for producing a fibrous material web in an apparatus that includes at least one shoe press having at least one drying cylinder and a shoe press unit which are arranged to form a pressing nip elongated in a web travel direction, at least one suctioned apparatus arranged before the at least one shoe press relative to the web travel direction, and an overpressure device associated with the at least one suctioned apparatus. The process includes guiding the fibrous material web over the at least one suctioned apparatus, and subjecting the fibrous material web to an overpressure while is it guided over the at least one suctioned apparatus.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.